1. Field of the Invention
The present invention relates to an image forming apparatus for forming images by the use of sheet materials and to a sheet cassette for use in such an image forming apparatus.
2. Description of the Prior Art
Japanese Patent Laid-open Application No. 63-11936 discloses a film cassette for use in a printer or the like. When the film cassette accommodating a plurality of sheet films has been charged into, for example, a printer, an end portion of a cover of the cassette protrudes out of the printer. The cassette can be opened by manually drawing the end portion for separation of the cover from the cassette. As a result, the cassette can feed the sheet films sheet by sheet under vacuum.
However, after the cover has once been removed from the cassette, it is impossible to cover the cassette with the cover again or to apply the cover onto the cassette. Accordingly, it is substantially impossible to perform the printing using films different in size from those accommodated in the cassette. In such a case, the cassette must be once removed from the printer and replacement of films is required.
In particular, when the films are made of a photosensitive material or materials, the film replacement must be conducted in a darkroom. This work is considerably troublesome.